Conventionally, an immunoassay utilizing an immunoreaction has been proposed as a method for detecting or quantitatively determining a trace substance, etc. in the environment. As the general measurement method for the immunoassay, for example, enzyme-linked immunosorbent assay (ELISA) and immunochromatography are known.
These methods require an operation of labeling a biological substance with a fluorescent substance, etc. and therefore, studies are being made on an analyte-measuring sensor that can be more easily and simply produced. For example, there has been proposed a biosensor containing a molecular recognition component capable of specifically reacting with a measurement target analyte, a stimulus-responsive polymer whose volume is changed by a reaction of the measurement target analyte and the molecular recognition component, and a metal particle having an average particle diameter of 0.2 to 200 nm, which varies in the intensity of localized surface plasmon resonance with the volume change of the stimulus-responsive polymer, wherein the metal particle and the molecular recognition component are fixed to the stimulus-responsive polymer (see, for example, Patent Document 1).